earth day

3. a colorless unstable toxic gas with a pungent odor and powerful oxidizing properties, formed from oxygen by electrical discharges or ultraviolet light. It differs from normal oxygen (O2) in having three atoms in its molecule (O3)
4. reuse (discarded objects or material) in such a way as to create a product of higher quality or value than the origina
7. protect (something, especially an environmentally or culturally important place or thing) from harm or destruction
9. the branch of biology that deals with the relations of organisms to one another and to their physical surroundings.
12. a geographic area where plants, animals, and other organisms, as well as weather and landscape, work together to form a bubble of life
13. the natural home or environment of an animal, plant, or other organism
14. decayed organic material used as a plant fertilizer
16. (of a contract, agreement, etc.) capable of being renewed.
18. able to be maintained at a certain rate or level.
19. contaminate (water, air, or a place) with harmful or poisonous substances.

1. a mixture of gases that surrounds the Earth
2. convert (waste) into reusable material
5. the surroundings or conditions in which a person, animal, or plant lives or operates.
6. maintain (something) in its original or existing state
8. something sent forth by emitting
10. relating to or derived from living matter
11. trash, wastepaper, or garbage
15. relating to or determined by the sun
17. (of a species, family, or other group of animals or plants) having no living members; no longer in existence
20. place to dispose of refuse and other waste material by burying it and covering it over with soil, especially as a method of filling in or extending usable land.